You'll find a thousand and one opinions on this topic here for sure...the one constant theme you'll see over and again is the idea to upgrade gradually (one component at a time).
I'd start with a set of stable loads from Tork Lift for sure...again a common first step, that you can install easily for very little investment. Then see how that goes.
If you still aren't happy consider a set of Timbrens! These are airless airbags that are install an forget (like the stable loads), and you can install yourself for very little investment. My personnel opinion is that air bags is kind of the old way of doing things....there are better products out there now that make air bags obsolete.
Once you've tested that you might want to consider rear sway bars, a leaf spring pack rebuild (best option but will run about $1400), new shocks...I like Bliesteins, 19.5 wheels and tires that are G or better rated! Certainly you should have E rated tires on your truck already at a minimum!
Hope that helps...feel free to PM me too if you want!